The prognostic value of small-sized platelet aggregates in unstable angina: Detection by a novel laser-light scattering method

Platelet activation plays a pivotal role in the pathogenesis of acute coron ary syndromes. This study was designed to evaluate the platelet aggregabili ty in patients with unstable angina using a new aggregometer with laser-lig ht scattering. We also examined whether there was a relationship between th ese platelet aggregabilities and unfavorable outcome during in-hospital sta y. We measured platelet aggregability, in particular small-sized platelet a ggregates in 31 patients with unstable angina, 31 patients with stable exer tional angina, and 30 patients with chest pain syndrome. The patients with unstable angina were divided into two groups by their cardiac events during in-hospital stay, cardiac events (+)(n = 11) group and cardiac events ( -) (n = 20) group. On admission, the number of small-sized platelet aggregates (V) was higher in patients with unstable angina (3.0+/-0.5 x 10(4)) than i n those with stable exertional angina (1.4+/-0.3 x 10(4), P = .017) and che st pain syndrome (0.7+/-0.2 x 10(4), P = .0003). The number of small-sized platelet aggregates was higher in the cardiac events (+) group than in the cardiac events (-) group (5.5+/-0.9 x 10(4) vs. 1.6+/-0.4 x 10(4), P = .000 1). A previous study elucidated that small-sized platelet aggregates ultima tely developed into medium-sized and large-sized aggregates as platelet agg regation proceeds. Therefore, the production of small-sized platelet aggreg ates is more sensitive for hyperaggregability. Furthermore, the production of small-sized platelet aggregates increased significantly in patients with unstable angina than in those with stable exertional angina and chest pain syndrome. These findings suggest that a tendency toward thrombus formation increases markedly in patients with unstable angina and increased number o f small-sized platelet aggregates on admission predicts poor prognosis duri ng in-hospital stay in patients with unstable angina. (C) 2001 Elsevier Sci ence Ltd. All rights reserved.